1. Field of Invention
The present invention generally relates to devices for guiding electron beams and, more particularly, is directed towards a dielectric guide for electron beam transport.
2. Description of the Prior Art
Propogation of electron beams for an appreciable length in a vacuum enclosure is inefficient unless some form of guiding field is used. The reason for such inefficiency is due to the repulsive space charge forces associated with the electrical charge on each electron that cause the beam to expand outwardly in the radial direction. The beam strikes the walls of the vacuum envelope and is lost. Several devices have been designed for controlling radial expansion of the electron beam. In one device, which has limited application, the electrical charge of the electron beam is neutralized by means of a background plasma. The self-magnetic field of the beam causes it to pinch inwardly for improving transport efficiency. Another device employs magnetic guide fields. Generally, a solenoidal field is used and the transverse motion of the beam is limited to a rotational mode rather than a radial mode. Under certain circumstances, efficient beam propogation is possible with the use of rather large magnetic fields. Magnetic field devices suffer from the disadvantage that the cost of the solenoid necessary to generate the magnetic field is excessively high and comparable to the cost of the main beam accelerator. Furthermore, there are situations in which it is desired not to have magnetic fields present, whereby magnetic field devices have limited application. A need has arisen for an inexpensive and efficient device of general application for electron beam transport in a vacuum which requires neither control of a background plasma environment nor costly equipment to provide guide fields.